Photosensitive sheet



United States Patent 2,967,105 PHOTOSENSITIVE SHEET Robert A. Peters,New York, N.Y., assignor to Stupa gorporatlon, New York, N.Y., acorporation of New 7 ork This invention relates to a photosensitivesheet on which a positive or a negative reproduction may be formed uponphotographic exposure to light of significantly greater intensity thansunlight but which can be exposed to sunlight before or after such highintensity photographic exposure without adverse color change, and tomethods of preparing and using such photosensitive sheets.

Heretofore the bromides and iodides of heavy metals such as silver andgold have been the preferred photosensitive materials by reason of theirready decomposition under the influence of light. Ferrocyanide compoundshave been employed for blueprints but have required an aqueousdevelopment. Certain organic compounds such as diazo materials have beensufiiciently sensitive to ultraviolet light to be suitable for oflicercproductions. These diazo papers have generally had the disadvantage ofrequiring development. under the influence of ammonia gas or equivalentreagent. Altho there have been certain proposals in the patentliterature relating to diazo papers which provide prints upon exposureto ultraviolet light and without any kind of development whatsoever,there has been no widespread tommercial use of the photographic paperrequiring no development.

In accordance with the present invention a photographic image is formedupon a suitably prepared photosensitive sheet under the influence oflight having an intensity significantly greater than that of sunlight.After the formation of such photographic image, and without developmentstep it can be handled in a normal manner without being extremelysensitive to fading or other color changes attributable to the action ofsunlight. The composition of the photosensitive sheet is such that thephotosensitive components are capable of forming two kinds ofdecomposition products. One of the decomposition products is black orsimilar dark color and the other decomposition product is white, paleyellow, transparent, and/or otherwise contrasting to the dark color ofthe other decomposition product. If the photosensitive sheet is designedto provide a negative, so that the decomposition product resulting fromthe high intensity illumination is dark colored, then the exposure ofthe photosensitive sheet to sunlight does not bring about the formationof any dark colored material. The negative image resulting from the highintensity exposure can be subjected to sunlight for an indefinite periodof time but to the extent that the sunlight brings about anydecomposition of the photosensitive components of the negative no fadingof the negative results by reason 0. the substantially white colorand/or transparency of the decomposition product from exposure to lightof the intensity of sunlight.

In certain embodiments of the present invention the photographic sheetcomprises organometallic compounds as the photosensitive component.Under the influence of light, and particularly under the influence ofultraviolet light the chemical bond between a carbon of an organic groupand the metal of the organometallic compound and/or the bond between twometal atoms'of an organometallic compound containing a plurality ofmetal atoms is broken. This light-induced breaking of a bond in anorganometallic forms reactive fragments which can participate in theformation of decomposition products. The composition of the photographicsheet can comprise material tending to form transparent and/or whitedecomposition products if the rate of photochemical decomposition of theorganometallic compound is slow but capable of forming dark coloreddecomposition products if the rate of decomposition of theorganometallic compound is-sufiiciently rapid.

In preferred embodiments of the present invention the photographic sheetcontains three reactive ingredients, namely, bis(tricyclohexyllead), anorganic'sulfur compound, and an organic oxygen compound. It is possiblethat the decomposition product resulting from the high intensityillumination partake of the nature of lead sulfide, a dark coloredmaterial. It is possible that the photo decomposition product from lowintensity exposure partake of the nature of lead oxide which is of apale yellow color. However, the beneficial results of the presentinvention are useful without regard to the correctness of thistheoretical explanation of the phenomena.

It has been noted that oflice reproduction prints or engineering printsshould comply with requirements such as:

(1) Good prints should be obtainable by moderately short exposures ofabout 10 second. Oflice print exposures are ordinarily within the rangeof from 5 seconds (short) to about 30 seconds (long). An exposure ofabout 2 seconds, altho very short for office reproduction prints, isstill of a very much higher order of magnitude than the of a second orof a second or other brief exposure required in motion picturephotography.

(2) The image resulting in the office print should provide sufiicientcontrast between the dark and. light portions that no difliculty wouldbe encountered in reading the print.

(3) Neither the light nor the dark portions of the oflice print shouldundergo any change making them less readable after prolonged exposure tosunlight.

(4) The unexposed paper should be sufliciently resistant to aging thatperiods of the magnitude of six months to a year between manufacture andexposure could cause no significant difliculty.

An oflice reproduction paper must not only provide a moderately shortexposure; adequate contrast, sunlight stability and storage stability,as respectively outlined previously, but it must provide the oflicereproduction at a low cost competitive with the diazo reproductions.Only a single molecule is photochemically decomposed by one quantum oflight in the ordinary photochemical decomposition. If the reactionmechanism involves the formation of free radicals, the free radicalfragments are capable of participating in a chain reaction providing amany fold increase in the number of atoms elfected by a single quantumof light. Thus a mixture of hydrogen and chlorine may be inert in thedark but exploded by exposure to a small amount of light. The lightdissociates the chlorine molecule into chlorine atoms and the chlorineatom is a free radical initiating a chain reaction. Benzoyl peroxidedecomposes under the influence of ultraviolet light to form freeradicals which can participate in chain reactions.

Some of the earliest and most detailed work concerning the nature offree radicals and their capacity for bringing about chain reactionsresulted from the thermal decomposition of organometallic compounds butthere have been few studies of the photochemical decomposition oforganometallic compounds.

Bis(tricyclohexyllead) (CH13)3Pb-Pb(C I'In) is a solid which is somewhatsensitive to sunlight but which Patented Jan. 3, 1961' 3 can be storedin subdued light. Earlier workers sometimes called this compoundtricyclohexylplumbane.

In the development of the present invention certain novel measurementswere made which helped to prove the feasibility of a photographic sheetsensitive only to high intensity light. It is helpful to understand theresults of exposing solutions of hexacyclohexyldiplumbane to ultraviolet light at various distances from a blueprinting lamp. A saturatedsolution of hexacyclohexyldiplumbane in cyclohexane was prepared. Aseries of cuvettes, each containing 4 ml. of the saturated solution,were positioned at various distances from a lamp and were exposed for 30minutes to a blueprinting lamp of sufficient intensity to be designatedas a 60 watt per inch lamp. The sample of solution positioned 8 inchesfrom the lamp underwent a photographic decomposition to form a whiteprecipitate. The sample positioned 7 inches from the lamp formed aprecipitate which had a slight gray color. The sample of 4 ml. of thesaturated solution in the cuvette positioned 6 inches from the lampunderwent a decomposition resulting in a dark brown precipitate. Aconspicuously black precipitate formed in the sample positioned 5 inchesfrom the lamp. There appeared to be crystals of metallic lead in theprecipitate in the cuvette positioned one inch from the lamp. Theseprolonged exposures of the solution of the organome'tallic compound tohigh intensity ultraviolet light demonstrated not merely that the colorof the decomposition product was dependent upon the intensity of lightbut also that a very great change of color resulted from a relativelysmall change in the intensity of light within what can be designated thecritical range of intensity. Thus the intensity at 6 inches was onlyabout or 178% of the intensity at 8 inches. These novel measurementsmade it appropriate to formulate the goal of an oflice reproductionpaper which would form white decomposition products upon prolongedexposure to ultraviolet light content of bright sunlight but which wouldform dark colored decomposition products upon short exposure to anultraviolet lamp providing an intensity from about 2 to 10 times theultraviolet intensity of sunlight.

In the development of the present invention, it was established that notonly did hexacyclohexyldiplumbane possess a color change depending uponthe intensity of illumination but that the compositions containing components capable of reacting with the decomposition prod uct possessedthe outstanding advantage of undergoing a difierent kind ofphotochemical decomposition under high intensity illumination than underlow intensity illumination.

Sunlight does not contain significant amounts of light of X-ray wavelength but it does contain significant amounts of ultraviolet light.Most materials which are sensitive to ultraviolet light are not suitablefor use in photographic materials by reason of their sensitivity tosunlight. The relatively low intensity of the ultraviolet light ofsunlight can have elfect on most photosensitive materials over a verylong period of time which is very similar to the effect of exposure to ablueprinting lamp or other high intensity ultraviolet source for atypical exposure period such as from 2 to 30 seconds. phenomena offorming decomposition products of different colors accordingto whetherthe light intensity is merely of the order of bright sunlight orsignificantly greater makes it possible to prepare ofice prints which donot fade after prolonged exposure to sunlight, notwithstanding theabsence of any conventional developing Hexacyclohexyldiplumbane wasprepared by a method substantially the same as that of Kranse, Ber, 54,2060 The 4 (1921). A stirred mixture of magnesium turning: in 400 ml. ofdry ethyl ether was reacted with 163 g. (1 mol) of cyclohexylbromide.The Grignard solution of bromomagnesiumcyclohexane then was slowly addedto g. (0.45 mol, or a 33% excess) of lead chloride,

and thereafter the mixture was heated at reflux for from 4 to 24 hours.After hydrolysis, and evaporation of the ether, the solids wereextracted with hot benzene. Hexacyclohexyldiplumbane was recovered fromthe hot benzene solution by several techniques, such as by precipitationupon cooling of the hot solution. Based upon the consumption ofbromocyclohexane, the most expensive reactant, the average yield ofhexacyclohexyldiplumbane in a series of successful preparations wasgreater than 50%.

Instead of using a method characterized by the Grignard reagentcyclohexylmagnesiumbromide, other methods of established ,value in thepreparation of organometallic compounds can be utilized. For example,cyclohexyllithium could be reacted with lead chloride in pentane. Thepurified hexacyclohexyldiplumbane is a light canary yellow color.- Twoforms of crystals have been identified under the microscope, one beinggenerally hexagonal plates, and the other being of a shortfibrous natureor hair-like tubular crystals. In order to obtain optimumresults inphotosensitive sheets, it is advantageous to purify the crude product byfiltering the boiling benzene solution, distilling to remove about 20%of the benzene of the saturated filtrate, and allowing the thus-preparedsupersaturated solution to cool to rapidly deposit high purity crystals.

EXAMPLE II A polyethylene resin was found to have an average molecularweight of about 14,000 as measured by the intrinsic viscosity technique.A coating composition was prepared by mixing about 40 ml. of boilingtoluene, 10 g. of said polyethylene, and 10 g. ofhexacyclohexyldiplumbane. This coating composition was spread upon about18.5 square meters of a hard finish paper to provide a dry film of about1 micron thickness. After the evaporation of the toluene solvent, thecoating composition consisted of about equal parts by weightpolyethylene and hexacyclohexyldiplumbane. The 1 micron thickness of thecoating provided approximately 1.08 g./m. or about 2 pounds per 1000square yards. The thus prepared photosensitive sheet, when exposed for10 seconds at a distance of six inches from a blueprinting lamp (60watts per inch) provided negatives which were dark brown in color. Thusit was established that the combination of a resin andhexacyclohexyldiplumbane provided a photosensitive coating for a sheethaving attractive qualities for oflice and/or engineering prints.

EXAMPLE III The advantageous results of using a paper coated with amixture of an organometallic compound and a resin are not limited tocoatings containing polyethylene. A series of tests were conducted usingvarious resins, and noting the effect of a change in the choice ofresin.

A parallel series of tests were conducted using tetraethyllead as theorganometallic compound in place of hexacyclohexyldiplumbane.Tetraethyllead contains a relatively higher concentration of lead, andonly 2 g. of tetraethyllead (about 28% on an equamolar basis) were usedin place of the 10 g. of hexacyclohexyldiplumbane. By reason of the hightoxicity of tetraethyllead, this tetraethyllead was first adsorbed intoparticles of colloidal size silica powder, about 5 g. of silica powder(such as results from vapor phase hydration of silicon tetrachloride)being used to adsorb 2 g. of tetraethyllead. The 7 g. of mixture oftetraethyllead on silica were dispersed in the mixture of 10 g. of resinand 50 ml. of solvent to provide a coating composition.

The thin film of coating composition on paper was allowed to drythoroughly. The thus prepared photosensitive sheet was exposed forseconds to the ultra-violet light of a blueprinting lamp positioned 6inches from the paper. The results of the tests indicated the color andsunlight stability of the dark portion of the negative. Because thepaper was so remote (6 inches) from the lamp, and the intensity was nearthe lower limit of the critical range, some of the resins effectivelyinhibited the development of a dark color under these conditions.However these tests provided evidence that under exposure at distancessignificantly less than 6 inches from the blueprinting lamp somereproduction machines provide an exposure about 1 inch or less from thelamp satisfactorily dark colors would be obtained.

In each case, the 10 g. of resin and the organolead compound were mxedwith 50 ml. of solvent consisting of 40 ml. of methyl ethyl ketone and10 ml. of toluene. After said standard exposure at the 6 inch distance,the various photosensitive papers had colors as indicated in Table 1.

formulations. Thus the weight of organometallic compound per unit areawas approximately 16% as great in the photosensitive sheets using 6parts of resin to 1 part of photosensitive compound as in the sheetshaving the l/ 1 ratio. Because some of the sheets being tested containedlesser amounts of the photosensitive material, the papers were exposedat a distance of 4 inches from the blueprint lamp. In some instances theexposure was longer than 10 seconds, thus indicating that a commerciallysatisfactory photosensitive sheet would require relatively largeramounts of activator. The codes assigned to the evaluations of thequality of the resistance to fading of the dark color resulting from theexposure to a high flux of ultra violet light were: A, excellent; B,good; C, fair; D, noticeable fading; E, troublesome fading; and F,unsatisfactory by reason of fading. Any unsatisfactory discoloration ofthe white portion of the negative print upon prolonged aging in directsunlight was coded as sunlight sensitivity or SS. Data relating toselected examples of organo- Table 1 hexacyclohexyldiplumbanetetraethyllead resin color fading color fading polyvinyl chloride darkbrown very slight---- light brown-.- slight. polyvinyl alcohol browslight. yelloweopoly-PVA-PVC. light brown... some do polyrneth; lmethacrdark brown. very slight dark brown.-- Do. polyethylncrylnte d ..-.-doo.. Do. polybutylucrylate do Do. polybutylmethaerylata do do Do. ethylcellulose brow o light brown-.. some. cellulose acetate do some..- rowDo. cellulose acetobutyrate dark brown very slightlight brown-.. Do.polyacrylonitrlle.. brow some Do. buttylacrylate-cellulose acetobutymtemlxvery dark brown.. nono very slight.

ure. methyl methaerylate-cellulose acetate .----do Do.

mixture.

Using an emulsion of methylcellulose in water as the resin for thecoating composition made possible the prepmetallic compounds as thephotosensitive component of photosensitive sheets are set forth in Table2.

Table 2 resin to organo-metallic ratio Compound 1/1 p.ethyleue color 3/1p.ethylene color 2/1 PEA-CAB color 6/1 PBA-OAB colorhexaeyclohexyldiplumbane dark brown, B dark brown, B dark brown, B darkbrown, B. tetraethy ea dark brown, 0 brown, 0 hexaethyldi lumbnnelightrown, D light brown -.do Do. tetrapheuy ead light brown, D60.--. lightbrown, D60.-. light brown, 1360...- light brown, B60. hexaphenyldllumbanedo do do Do. tetrabutylle dark yellow dark yellow, 11 brown,brown, 0. diphenylleadsulfideblack, A 88.. black, A SS... block, A SS.tetraghenyltin brown, D130. brown, D140" brown, C140. tetra uty brown,D140. ----.do Do. hexsbutyldistannane-.- brown, D110... brown, 0100..brown, G100. hexacyelohexyldi brown, B20 brown, B20 brown, B20.dimethyltins do. 0 light brown, D20 light brown, 320.--- brown, 020.triphcnylarsenic light brown, D120... yellow, E120 yellow, 120 Ivlellow,120. triphenylantim0ny light brown. C120..- yellow, D120-.- row'n,(2120-- ght brown, C120. tributylantlmony--- brown, C100 brown, C100..-brown, 0100.- trlphenylblsmuth brown, 030 brown, B dark, C20 brown, 020.

aration of a hexacyclohexyldiplumbane paper which had a brown color witha noticeable tendency to fade after exposure. There was a similartendency for the brown negative resulting from the correspondingphotosensitive paper prepared from tetraethyl lead and a water emulsionof methyl cellulose.

EXAMPLE IV of equal parts of polybutylacrylate and celluloseacetobutyrate was the resin used in the 2/1 and 6/1 ratio By a series oftests it was shown that important advantages are achieved by preparingthe photosensitive sheet to include one'or more organometalliccompounds, each compound containing one or more metals selected from thegroup consisting of lead, tin, arsenic, antimony and bismuth. Althoughmany of the organometallic compounds of other metals can be decomposedby light of approprate wave length and intensity, none of such otherorganometallic compounds demonstrated a highly attractive combination ofproperties for photosensitive sheets in the tests conducted during thedevelopment of the present invention. However, there is reason tobelieve that organometallic compounds generally possess advantages asphotosensitive compounds by reason of the phenomena that the light tendsto decompose the metal-metal bond and/or organo-metallic bondpreferentially to any decomposition of a carbon-carbon bond in suchmolecules,

7 and because the reactive fragments resulting from the photochemicaldecomposition of an organometallic compound are capable of reactingrapidly in a manner dependent greatly upon the flux or intensity of theultraviolet light. Certain advantages are achieved by the use ofcompounds having a metal-metal bond. Certain advantages result from theuse of cyclohexyl derivatives. Aromatic derivatives are decomposed bylight with greater di.f-'

ficulty. Paraffinic derivatives are of intermediate photosensitivity.Novel measurements were made by taking the spectrograms of solutions ofvarious compounds on a Beckman ultra-violet spectrophotometer. Thecarbon tetrachloride solutions of a series of organolead compounds weresimilar in the there was nearly complete transmission-for a wide bandnearly complete adsorption of a wide band, with a relatively steep curveseparating the two zones on the spectrogram. The wave length of 50%transmission provides an important clue to the photosensitivity of anorganometallic compound. A significantly shorter ultra-violet wavelength characterized tetraphenyllead than hexacyclohexyldiplumbane.Tetraethyllead had an intermediate wave length at the point of 50%opacity.

EXAMPLE V The dark color resulting from the photographic exposure may beattributable either to metallic deposit or to a reaction product whichis more complex. In the development of the present invention it wasestablished that a variety of sulfur-containing organic compounds servedas activators for photographic sheets comprising organo-metalliccompounds. It is not known whether the metal forms mercaptides, metalsulfides, or other metalsulfur type of materials or whether thebeneficial effect is attributable to some catalytic or other phenomena.In any event, the photographic sheets containing controlled amounts ofactivators provide dark colors which are darker, less suseptible tofading, responsive to briefer pe- 8 cause of the desirability ofmarketing the photosensitive paper at a cost per square yard lower thanthe cost of either diazo paper or blueprint (ferrous ferricyanide)paper, it is desirable to use formulations providing an organometalliccompound content per 1000 square yards corresponding to less than aboutone pound of metal. A minimum concentration is equivalent to about 8ounces per 1000 square yards, and the maximum concentration (if cost isnot important) may be about 20 pounds of 10 metal (a correspondinglylarger amount of organo-metallic compound) per 1000 square yards.

Comparative experiments on extenders are difficult to interpret. It hasbeen found that the effectiveness of an activator as an accelerator issimilar to its effectiveness as an extender. The comparison of theaccelerator effectiveness is readily interpreted.

A series of tests were made using the same general formulation, andvarying the choice and concentration of the activator. All of theactivators listed herein have been shown to be useful in photosensitivesheets, but under the standard comparison tests several of them showvarying degrees of sunlight sensitivity. In the sunlight sensitivenegative prints, the light color, instead of retaining its initial whitecolor, underwent a darkening when exposed to bright sunlight for aprolonged period of time. The effect of aging, sometimes designated assunlight sensitivity, is designated in Table 3. A series of papers wereprepared by use of compositions consisting of: 10 g. ofhexacyclohexyldiplumbane, 5 g. polybutylacrylate, 5 g. toluene (or 20 g.of the stock mixture of these proportions); 10 g. celluloseacetobutyrate, g. methyl ethyl ketone (or g. of a second stock mixture);and the specified amount of the indicated activator. The image was inall cases sufiiciently black to be commercially satisfactory, but theexposure time necessary to achieve such result was measured. The dataare set forth in Table 3.

Table 3 amount of activator used in composition activator 0.1 g. 1.0 g.10.0 g.

isecondsi aging seconds! aging seconds aging flowers of sulfur 1darken---- 1 dark 1 darkens. z-mercapto bensothiazoline 3 slight.-." 3all ht- 2 little.

t thlophonnl 10 yellow-...- 6 ye iow.... 5 yellows.

tetrathiuramdisultide 50 v. s1. 30 slight"-.- 20 none. potassium ethylxanthoato- 20 darkens.-. 10 browns 10 browns. tetrathiuramtetra-sulfide--. 2o sllght---.- 20 sllght----.. 10 slight. potassiumethyl mnthoate I) darkens." 10 browns...- 10 browns. thinamharnidn 2oyellows.-.- 20 yel1ows. a0 yellows. dithiooxamide 30 do 30 do 20 Do.thioinslie aci 30 do 30 do 20 Do. potassium thlocarbon ate an blackens20 blackeus- 15 blackens. phosphorus pentasulflde so do 20 do photo-iaflammable. diphenylthiooarbazoue 20 no change. 20 no change. 20 nochange. thtosemicsrh 20 do 20 do 20 Do. 1,5 dlphenyl thiocarbohydrazide2o yellows..-- 20 yellows--.. 10 yellows.

riods of exposure, responsive to lower concentrations of organo-metalliccompound per unit area, responsive to lesser intensities of ultra-violetlight and/or possessing other advantages over photosensitive sheetswithout such activators.

Ordinarily the main purpose of including the organic sulfur activatorsin the composition is for the purpose of reducing the requirements forthe organo-metallic compound per unit area, but because the otherefiects have been established, the term activator is more appropriatethan the term extender. Organometallic compounds are generallyexpensive. Because of this high cost, and be- Exteusive experimentationof the type illustrated in Table 3 established that the activator shouldbe a material containing sulfur, selenium or tellurium, and thatparticular advantages accrued from the use of a material have afunctional group selected from the class consisting of 8, S=, S SH-,

SH -=8, -(i:8 which can also be described respectively as elementalsulfur, sulfide and polysulfide, thiol, thioether, thione (comprisingalso thials and thiocarboxylic groups) and dithiocarboxylic groups.

9 EXAMPLE V! In obtaining a colorless and/or white product from thephoto-decomposition of organometallic compounds, the presence of oxygen,peroxides, carbon dioxide, and re- 10 bination with 100 mg. of either 2mercaptobenzothiazoline or potassium ethyl xanthoate.

EXAMPLE VII lated materials are especially advantageous. Possibly theAlthough organo'metanic P l f are the F f reactive fragments resultingfrom the photochemical de- Q P the Present Invention P composition of anorganometallic compound have a uve a be ye to aehleYe the strongtendency to react relatively slowly with any traces vantageousfombmatwnP Provtdlhg q t s 001018 of oxygen or related materials present in theenvironunder Influence of light havlhg ah Intensity greater ment, sothat this is the predominating reaction except than suhhght, but not fflfter adversely affected by under those conditions in which the rate ofphotochem- Prolonged exposure Sunlight, twlthstandmg the abicaldecomposition of the organo-metallic compound is Sence f any chemlcaltreatment fixing antil/01' so rapid that free metal and/or metal-sulfurcompounds hghave an opportunity to form A positive paper 1s prepared bycoating a paper with one of the several methods of obtaining aphotosensi 5 a composition consisting of 10 parts of polybutylacrylate,tive sheet having an overall balance of attractive properto Ph ofcellulose acetobutyrate, 5 parts o pp ties is to coat paper with acomposition comprising an acetyhde, and 5 Parts of shctflhyl azide, and75 p r of organometallic compound, a sulfur-containing activator,tetrah3fdrfurah- The P pe Is coated in e dark- T e and anoxygen-containing inhibitor. The maximum con- Paper lohded e ordmar Ycamera and the Picture centration of the activator is desirably notgreater than 1S talfeh three tunes t number of a h bu bs conthat of theorganometauic compound The optimum vent onally used. The intense lightdecomposes the concentration of the inhibitor in many compositions is he z q component of the photosensitive Sheet, P within the range from 1.0to 10% of the concentration Vldlhg l'eeetlve fragments Combining withthe copper to of the activator. The maximum concentration of inhibform awhlte background metel'lal the White Portions itor should be less thanthe organometallic concentration. of the p The Sheet is e e oved fromthe cam- In a series of tests papers were prepared using some era, andthe effect Of the sunlight on the balance Of the of the formulations ofTable 3, but adding measured Pflht is to form a black copper image- TheSunlight amounts of benzoyl peroxide. The composition was prebringsehotlt the deeolhposittoh of the pp aeetylide pared by mixing: asolution consisting of 10 g. of celluexcept those areas In which the ppslleciflnaie lose acetobutyrate, 40 g. of methyl ethyl ketone, the bindsthe copper in a form insensitive to Sunlight. Indesignated amount of thedesignated activator, and the stead of pp aeetyhde, lead azide, Silveracetylide, d i d amount f b l id d 10 f h related light-sensitive metalcompound which can react cyclohexyldiplumbane, 5 g. of polybutylacrylateand 5 g. with a dibasic organic acid or chelating compound to oftoluene. A film about 1 mil thick was formed on form a White Compoundinsensitive to Sunlight may be paper. The coated paper was exposed to ablueprintin employed. Instead of succinyl azide, any light sensitive l fa ffi i i d of i e t id a reasonchelator, such as the azide ofethylenediamine tetraacetic ably black image, and thereafter thestability of the white ac d may be employed. portions of the negativeprint to bright sunlight was Obviously various modifications of theinvention are measured. Data relating to some of these tests are shown40 possible without departing from the scope of the invenin Table 4.tion as set forth in the appended claim.

Table 4 Quantity of Bemoyl Peroxideg. activator 10 mg. mg. 100 mg. 200mg.

seconds aged color seconds aged color seconds aged color seconds agedcolor 0.1 flowers ofsuliur 2 light brown. 2 yellow brown. 2 yellowbrown. 3 yellow. 1.0 sulfur 2 black 2 dark brown..- 2 dark brown 3 allowbro 10.0 do 2 .do 2 black... 3 black 3 rown. 0.1 Z-merca tobenzo 3 brown3 tan..- 3 yellow a whim,

thlazoine. 1.0 do 3 do 3 brown. 5 tan 5 yellow, 10.0 -.d0 2 ....do 2 .do3 yellow 5 paleyellow, 0.1 potassium ethyl 20 tan 5 tan 10 do 20 white.

xanthoate. 1.0 potassium salt of 10 brown to brown 10 brown 10 yellow.

ethgl xanthole 10.0.--.- po t sslumethyl 5 ----do 5 do 5 do to brown.

xanthoate.

The invention claimed is:

A photosensitive sheet consisting essentially of a strong backing and aphotosensitive composition uniformly coated on the backing, saidphotosensitive composition consisting essentially of:bis(tricyclohexyllead) in a concentration from 8 ounces to 20 pounds per1000 square yards of photosensitive sheet; an activator in aconcentration within the range from 1% to of the concentration of thebis(tricyclohexyllead), said activator being selected from the groupconsisting of sulfur, organic thiols, organic sulfides, and salts oforganic dithio- 11 carboxylic acids; and a peroxide in a concentrationwith- 2,095,839 in the range from 1% to 100% of the activator. 2,219,463

2,414,839 References Cited in the file of this patent 2,4 UNITED STATESPATENTS 5 1,880,503 Sheppard et a1. Oct. 4, 1932 217121996 1,897,843Hickman et a1. Feb. 14, 1933 1,939,232 Sheppard et a1. Dec. 12, 19331,976,302 Sheppard et a1. Oct. 9, 1934 10 2,057,016 DeBoer et al. Oct.13, 1936 12 Sheppard et a1. Oct. .2, 1937 Yngve Oct. 29, 1940 SchoenIan. 28, 1947 Chalkley May 18, 1948 Baurnann et a1. July 13, 1954 EggertMar. 1, 1955 Elliot July 12, 1955 OTHER REFERENCES Coates:Organo-Metallic Compounds, John Wiley, NY. (1956), page 141.

